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Dan, Master Tech and Repair Facility Trainer
Category: TV
Satisfied Customers: 7180
Experience:  USAF trained; A.A.S Electronics; A.A.S. Education; Currently teaching advanced troubleshooting and repair for the DoD.
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50 inch LG Plasma TV has sound but no picture. What is the

Resolved Question:

50 inch LG Plasma TV has sound but no picture. What is the fix. Have back of tv off which board and what part do I change?Modle # XXXXX
Submitted: 6 years ago.
Category: TV
Expert:  Dan replied 6 years ago.


Thanks for the question. My name is Dan.


Usually this is a Ysus issue (LGs are pretty notorious for this). But let's see if we can narrow it down for sure.


Looking inside the TV, there should be 3 large boards with heatsinks attached... and a few smaller ones. Turn the TV on and let is sit for 20 minutes (enough time for the TV to warm up). Then, touch the heatsinks (take care not to touch anything else).


Are any of the heatsinks cold? If so, which ones... on which board?


Edited by Dan T. on 11/8/2010 at 12:21 PM EST
Customer: replied 6 years ago.
the only one's that are heating up, are on the center board. The one on the far left on the center board is not heating up.
Customer: replied 6 years ago.
Rely switch DEGSDT-5-105DMR on the same cuircit board is clicking on and off
Expert:  Dan replied 6 years ago.
The Ysus should be on the far left (looking at the TV from the rear; rear panel removed). The Zsus should be on the right. The Ysus should be larger than the Zsus; both should have heatsinks. The Ysus should have 2 scan boards attached... probably running vertically on the far left edge (again, viewing from the rear).

After the warm up, are the Ysus heatsinks cold?
Customer: replied 6 years ago.
Expert:  Dan replied 6 years ago.
Consider replacing the Ysus. A new board is about $125 and can be purchased here. Also understand this could be a PSU (power supply unit) malfunction, or even possibly the plasma panel itself. Should you decide on a DIY here, also consider looking into a service manual.

Dan and 4 other TV Specialists are ready to help you
Customer: replied 6 years ago.
how do i check the ysus can i change the bad part
Expert:  Dan replied 6 years ago.
Without a solid electronics skill set and proper measurement tools, there aren't any tests you can do to confirm serviceability... only the heat sink "touch test." This is a down and dirty method, so to speak... shops use it everyday. Heck, the DoD often teaches this method in basic electronics school. That said, if you're unfamiliar with TV innards, consider leaving the Ysus replacement for a qualified tech. Else, it's a few screws and cables. If you have experience working inside TVs, go for it (consider purchasing a service manual).

Customer: replied 6 years ago.
i am a tech working in elk hills Ca i can change the ysus i just need to get one and manuel send one
Expert:  Dan replied 6 years ago.
I sent a link earlier for the Ysus... click that for the part. There are a few good sites for service manuals...,, or consider contacting LG directly.

Customer: replied 6 years ago.
thanks dan